Caucasian "whiteness" did not necessarily evolve in the Caucasus, in fact, I think that region was far too close to the center of the superhighway that was the N eurasian steppes, to be where it developed. I think it happened in central europe (Carpatho-Danubia) where there was actually some isolation relative to the bulk of the rest of humanity. Or, we picked it up from Neandertals, and Eastasians from erectus--hence why each race has different genetic "avenues" they used to achieve this cold-adaptation.